Control device for hybrid vehicle

ABSTRACT

A control device for a hybrid vehicle which enables an improvement in fuel consumption by means of a cylinder deactivation operation while maintaining brake performance. The hybrid vehicle has an engine (E) and a motor (M) for outputting power for driving the vehicle, wherein a regenerative brake is used during deceleration traveling of the vehicle in accordance with a deceleration state thereof, and the engine (E) includes at least one deactivatable cylinder which is deactivatable during deceleration traveling of the vehicle. The control device comprises: a deactivation determining section for determining whether the deactivatable cylinder is allowed to be deactivated in accordance with a traveling state of the vehicle; a deactivation cancellation determining section for canceling cylinder deactivation during deactivation operation; an intake pressure sensor (S 1 ); a master vac negative pressure sensor (S 3 ); and a control valve ( 34 ) for opening/closing a secondary air passage ( 33 ) for providing auxiliary air into the intake passage ( 30 ), wherein the control valve ( 34 ) is closed when the intake pressure is a negative value lower than a predetermined threshold during deceleration traveling of the vehicle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control device for a parallel typehybrid vehicle having an engine with deactivatable cylinders, and inparticular, relates to a control device for a hybrid vehicle, whichenables an improvement in fuel consumption while maintaining brakeperformance.

2. Description of the Related Art

A hybrid vehicle having not only an engine but also an electric motor asthe drive source has been known in the art. As a type of hybrid vehicle,a parallel hybrid vehicle is known that uses an electric motor as anauxiliary drive source for assisting the engine output.

In the parallel hybrid vehicle, the power of the engine is assisted bythe electric motor during acceleration traveling. On the other hand,during deceleration traveling, the battery and the like are charged viaa deceleration regenerating operation. According to various controloperations including the above, the remaining battery charge (remainingelectric energy) of the battery is maintained while also satisfying thedriver's demands. Because the drive train of the parallel hybrid vehiclecomprises the engine and the motor coupled to the engine in series, thewhole system is simple in structure, light in weight, and has greatflexibility for installation in the vehicle.

As variations of the parallel hybrid vehicle, two types of hybridvehicles are known; one is disclosed in, for example, JapaneseUnexamined Patent Application, First Publication No. 2000-97068, inwhich a clutch is disposed between the engine and the motor in order toeliminate the effect of engine friction (i.e., engine brake) during thedeceleration regenerating operation; the other is disclosed in, forexample, Japanese Unexamined Patent Application, First Publication No.2000-125405, in which the engine, the motor, and a transmission aredirectly connected in series in order to ultimately simplify thestructure.

The hybrid vehicle of the former type exhibits disadvantages in that theinstallability of the power train is degraded due to the complexity inthe constitution of the clutch, and the transmission efficiency of thepower train may be reduced during normal traveling as well due to theuse of the clutch. On the other hand, the hybrid vehicle of the lattertype exhibits a disadvantage in that the driving power assisted by theelectric motor (assisted power) is restricted because regeneratedelectric energy is reduced due to the aforementioned engine friction.

As another measure to reduce the engine friction during deceleration, anelectronic control throttle mechanism may be used which controls athrottle valve to be open during deceleration so as to greatly reducethe pumping loss and to increase the regenerative energy; however, aconsiderable amount of new air directly flows into the exhaust systemduring deceleration, which may lower the temperature of a catalyst andan air flow sensor and could cause inappropriate exhaust gas control.

A cylinder deactivation technique has been proposed to solve the aboveproblem; however, the cylinder deactivation period is limited in orderto retain a sufficient negative pressure in the master vac for the brakesystem, and consequently, not much regenerative energy can be saved bythe reduction of engine friction.

SUMMARY OF THE INVENTION

In consideration of the above circumstances, an objective of the presentinvention is to provide a control device for a hybrid vehicle which canprovide a more frequent cylinder deactivation operation whilemaintaining the brake performance and enables a great improvement in thefuel consumption of the vehicle due to a reduction of engine friction.

To this end, a first aspect of the present invention provides a controldevice for a hybrid vehicle having an engine and a motor for outputtingpower for driving the vehicle, wherein a regenerative brake is usedduring deceleration traveling of the vehicle in accordance with adeceleration state thereof, and the engine includes at least onedeactivatable cylinder which is deactivatable during decelerationtraveling of the vehicle. The control device comprises: a deactivationdetermining section for determining whether the deactivatable cylinderis allowed to be deactivated in accordance with a traveling state of thevehicle; a deactivation cancellation determining section for cancelingcylinder deactivation during deactivation operation; an intake pressuresensing section for measuring air pressure in an intake passage of theengine; and a control valve operating section for opening/closing asecondary air passage of the engine for providing auxiliary air into theintake passage by operating a secondary air valve, wherein the controlvalve operating section operates the secondary air valve so as to closethe secondary air passage when the intake pressure measured by theintake pressure sensing section is a negative value lower than apredetermined first threshold during deceleration traveling of thevehicle.

Accordingly, because the control valve operating section operates thesecondary air valve so as to close the secondary air passage when theintake pressure is a negative value lower than the predetermined firstthreshold at the instance of starting deceleration traveling, the intakedepression of the engine can be efficiently utilized to ensure thenegative pressure in the master vac is sufficiently low.

A second aspect of the present invention provides a control device for ahybrid vehicle having an engine and a motor for outputting power fordriving the vehicle, wherein a regenerative brake is used duringdeceleration traveling of the vehicle in accordance with a decelerationstate thereof, and the engine includes at least one deactivatablecylinder which is deactivatable during deceleration traveling of thevehicle. The control device comprises: a deactivation determiningsection for determining whether the deactivatable cylinder is allowed tobe deactivated in accordance with a traveling state of the vehicle; adeactivation cancellation determining section for canceling cylinderdeactivation during deactivation operation; a master vac negativepressure sensing section for measuring negative pressure in a master vacwhich communicates with an intake passage of the engine and whichassists a braking force by means of intake depression in accordance withthe braking operation by the operator of the vehicle; and a controlvalve operating section for opening/closing a secondary air passage ofthe engine for providing auxiliary air into the intake passage byoperating a secondary air valve, wherein the control valve operatingsection operates the secondary air valve so as to close the secondaryair passage when the negative pressure in the master vac measured by themaster vac negative pressure sensing section is a negative value higherthan a predetermined second threshold during deceleration traveling ofthe vehicle.

Accordingly, because the control valve operating section operates thesecondary air valve so as to close the secondary air passage when thenegative pressure in the master vac is a negative value higher than thepredetermined second threshold at the instance of starting decelerationtraveling, the intake depression of the engine can be efficientlyutilized to decrease the negative pressure in the master vac to asufficiently low value.

A third aspect of the present invention provides a control device for ahybrid vehicle having an engine and a motor for outputting power fordriving the vehicle, wherein a regenerative brake is used duringdeceleration traveling of the vehicle in accordance with a decelerationstate thereof, and the engine includes at least one deactivatablecylinder which is deactivatable during deceleration traveling of thevehicle. The control device comprises: a deactivation determiningsection for determining whether the deactivatable cylinder is allowed tobe deactivated in accordance with a traveling state of the vehicle; adeactivation cancellation determining section for canceling cylinderdeactivation during deactivation operation; an intake pressure sensingsection for measuring air pressure in an intake passage of the engine; amaster vac negative pressure sensing section for measuring negativepressure in a master vac which communicates with an intake passage ofthe engine and which assists a braking force by means of intakedepression in accordance with the braking operation by the operator ofthe vehicle; and a control valve operating section for opening/closing asecondary air passage of the engine for providing auxiliary air into theintake passage by operating a secondary air valve, wherein the controlvalve operating section operates the secondary air valve so as to closethe secondary air passage when the intake pressure measured by theintake pressure sensing section is a negative value lower than apredetermined first threshold and the negative pressure in the mastervac measured by the master vac negative pressure sensing section is anegative value higher than a predetermined second threshold duringdeceleration traveling of the vehicle.

Accordingly, the intake depression of the engine can be efficientlyutilized to decrease the negative pressure in the master vac to asufficiently low value when the negative pressure in the master vac isnot sufficiently low prior to the cylinder deactivation operation.

A fourth aspect of the present invention provides a control device for ahybrid vehicle, wherein the control valve operating section operates thesecondary air valve so as to close the secondary air passage whencylinder deactivation is prohibited by the deactivation determiningsection.

Accordingly, the secondary air valve is closed so that the intakenegative pressure can be ensured to be sufficiently low prior to thecylinder deactivation operation.

A fifth aspect of the present invention provides a control device for ahybrid vehicle, wherein the predetermined first threshold is determinedin accordance with a running speed of the engine.

Accordingly, the predetermined first threshold is appropriatelydetermined in accordance with the running speed of the engine.

A sixth aspect of the present invention provides a control device for ahybrid vehicle, wherein the second threshold is determined in accordancewith a traveling speed of the vehicle.

Accordingly, the second threshold is appropriately determined inaccordance with the traveling speed of the vehicle, where the secondthreshold relates to the negative pressure in the master vac which isutilized to decrease the traveling speed of the vehicle.

A seventh aspect of the present invention provides a control device fora hybrid vehicle, wherein the control system further comprises adeceleration state determining section for determining a degree ofdeceleration of the vehicle, and wherein the deactivation cancellationdetermining section cancels the cylinder deactivation when the degree ofdeceleration exceeds a predetermined value.

Accordingly, stopping of the vehicle may be set to have highestpriority, therefore, a cylinder deactivation operation is not executedwhen the degree of deceleration is considered to be great.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the general structure of a hybridvehicle in an embodiment according to the present invention.

FIG. 2 is a flowchart showing the operation for switching into acylinder deactivation operation in an embodiment of the presentinvention.

FIG. 3 is a flowchart showing the operation for determining whether thepre-deactivation conditions permitting the cylinder deactivationoperation are satisfied in an embodiment of the present invention.

FIG. 4 is a flowchart showing the operation for determining whether thedeactivation cancellation conditions are satisfied in an embodiment ofthe present invention.

FIG. 5 is a flowchart showing the operation for selecting air controlmode in an embodiment of the present invention.

FIG. 6 is also a flowchart showing the operation for selecting aircontrol mode in an embodiment of the present invention.

FIG. 7 is a flowchart showing the operation for selecting air controlmode in another embodiment of the present invention.

FIG. 8 is a front view showing a variable valve timing mechanism used inan embodiment of the present invention.

FIGS. 9A and 9B show the variable valve timing mechanism used in theembodiment of the present invention; in particular, FIG. 9A shows across-section of the main part of the variable valve timing mechanism ina cylinder activation state, and FIG. 9B shows a cross-section of themain part of the variable valve timing mechanism in a cylinderdeactivation state.

FIG. 10 is an enlarged view of the main part in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be explainedwith reference to the appended drawings.

FIG. 1 is a block diagram schematically illustrating a parallel hybridvehicle to which the embodiments of the present invention are applied,and which comprises an engine E, an electric motor M, and a transmissionT directly coupled to each other in series. The driving force generatedby both the engine E and the electric motor M is transmitted via, forexample, a CVT (continuously variable transmission) as the transmissionT (the transmission T may be a manual transmission) to front wheels Wfas driving wheels.

When the driving force is transmitted from the driving wheels Wf to theelectric motor M during deceleration of the hybrid vehicle, the electricmotor M functions as a generator for applying a so-called regenerativebraking force to the vehicle, i.e., the kinetic energy of the vehicle isrecovered and stored as electric energy.

The driving of the motor M and the regenerating operation of the motor Mare controlled by a power drive unit (PDU) 2 according to controlcommands from a motor CPU 1 M of a motor ECU 1. A high-voltage nickelmetal hydride battery 3 for sending and receiving electric energy to andfrom the motor M is connected to the power drive unit 2. The battery 3includes a plurality of modules connected in series, and in each module,a plurality of cell units are connected in series. The hybrid vehicleincludes a 12-volt auxiliary battery 4 for energizing variousaccessories. The auxiliary battery 4 is connected to the battery 3 via adownverter 5 or a DC-DC converter. The downverter 5, controlled by anFIECU 11 (a part of the control valve operating section), makes thevoltage from the battery 3 step-down and charges the auxiliary battery4. The motor ECU 1 comprises a battery CPU 1B for protecting the battery3 and calculating the remaining battery charge thereof. In addition, aCVTECU 21 is connected to the transmission T, which is a CVT, forcontrolling the same.

The FIECU 11 controls, in addition to the motor ECU 1 and the downverter5, a fuel supply amount controller (not shown) for controlling theamount of fuel supplied to the engine E, a starter motor (not shown),ignition timing, etc. To this end, the FIECU 11 receives various signalssuch as a signal from a speed sensor for sensing vehicle speed, a signalfrom an engine revolution speed sensor for sensing engine revolutionspeed, a signal from a shift position sensor for sensing the shiftposition of the transmission T, a signal from a brake switch fordetecting the operation of a brake pedal, a signal from a clutch switchfor detecting the operation of a clutch pedal, a signal from a throttleopening-degree sensor for sensing the degree of opening of a throttlevalve 32, a signal from an intake negative pressure sensor for sensingnegative pressure in the air-intake passage, a signal from a knockingsensor, and the like.

In FIG. 1, reference symbol BS indicates a booster associated with thebrake pedal, in which a master vac negative pressure sensor is providedfor sensing negative pressure in the brake master vac (hereinafterreferred to as master vac negative pressure). The master vac negativepressure sensor is connected to the FIECU 11.

For the purpose of clarification, only an intake negative pressuresensor S1 (a part of an intake pressure sensing section) provided in anair-intake passage 30, a throttle opening-degree sensor S2, a master vacnegative pressure sensor S3 (a part of the master vac negative pressuresensing section) provided with a communication passage 31 connected tothe air-intake passage 30, and a knocking sensor S4 are shown in FIG. 1.

The air-intake passage is provided with a secondary air passage 33 forair communication between the upstream portion with respect to thethrottle valve 32 and the downstream portion, and the secondary airpassage 33 is provided with a control valve 34 or a secondary aircontrol valve. The purpose of providing the secondary air passage 33 isto supply a small amount of air into the cylinders even when theair-intake passage 30 is completely closed by the throttle valve 32. Thecontrol valve 34 is controlled by means of the signal from the FIECU 11in accordance with the intake negative pressure measured by the intakenegative pressure sensor S1. A POIL (oil pressure) sensor S5, a solenoidof a spool valve 71, and a TOIL (oil temperature) sensor S6, all ofwhich will be explained below, are also connected to the FIECU 11. Theknocking sensors S4 are provided for detecting a misfire state in thecylinders having a variable valve timing mechanism VT.

The engine E includes three cylinders associated with the variable valvetiming mechanism VT on both an intake side and an exhaust side, and acylinder associated with a conventional valve mechanism which has norelation to the cylinder deactivation operation.

In other words, the engine E is a deactivatable engine in which theoperation state may be alternated between normal operation in which allfour cylinders including three deactivatable cylinders are active and acylinder deactivation operation in which three deactivatable cylindersare inactive. In the engine E, the operation of the intake valves IV andexhaust valves EV associated with the deactivatable cylinders can betemporarily stopped by means of the variable valve timing mechanism VT.

Next, the variable valve timing mechanism VT will be explained in detailwith reference to FIGS. 8 to 10.

FIG. 8 shows an example of an SOHC engine provided with the variablevalve timing mechanism VT which is adapted for a cylinder deactivationoperation. The cylinder (not shown) is provided with the intake valve IVand the exhaust valve EV which are biased by valve springs 51 in adirection which closes the intake port (not shown) and exhaust port (notshown), respectively. Reference symbol 52 indicates a lift cam providedon a camshaft 53. The lift cam 52 is engaged with an intake cam liftingrocker arm 54 a for lifting the intake valve and an exhaust cam liftingrocker arm 54 b for lifting the exhaust valve, both of which arerockably supported by a rocker arm shaft 62.

The rocker arm shaft 62 also supports valve operating rocker arms 55 aand 55 b in a rockable manner, which are located adjacent to the camlifting rocker arms 54 a and 54 b, and whose rocking ends press the topends of the intake valve IV and the exhaust valve EV, respectively, sothat the intake valve IV and the exhaust valve EV open their respectiveports. As shown in FIGS. 9A and 9B, the proximal ends (opposite the endscontacting the valves) of the valve operating rocker arms 55 a and 55 bare adapted so as to be able to engage a circular cam 531 provided onthe camshaft 53.

FIGS. 9A and 9B show, as an example, the cam lifting rocker arm 54 b andthe valve operating rocker arm 55 b provided in the exhaust valve side.

As shown in FIGS. 9A and 9B, a hydraulic chamber 56 is formed in the camlifting rocker arm 54 b and the valve operating rocker arm 55 b in acontinuous manner, which is located on the opposite side of the rockerarm shaft 62 with respect to the lift cam 52. The hydraulic chamber 56is provided with a pin 57 a and a disengaging pin 57 b both of which areslidable and biased toward the cam lifting rocker arm 54 b by means of apin spring 58.

The rocker arm shaft 62 is provided with, in its inside, a hydraulicpassage 59 which is divided into hydraulic passages 59 a and 59 b by apartition S. The hydraulic passage 59 a is connected to the hydraulicchamber 56 at the position where the disengaging pin 57 b is located viaan opening 60 of the hydraulic passage 59 b and a communication port 61in the cam lifting rocker arm 54 b. The hydraulic passage 59 b isconnected to the hydraulic chamber 56 at the position where the pin 57 ais located via an opening 60 of the hydraulic passage 59 a and acommunication port 61 in the valve operating rocker arm 55 b, and isadapted to be further connectable to a drain passage (not shown).

As shown in FIG. 9A, the pin 57 a is positioned by the pin spring 58 soas to bridge the cam lifting rocker arm 54 b and the valve operatingrocker arm 55 b when hydraulic pressure is not applied via the hydraulicpassage 59 b. On the other hand, when hydraulic pressure is applied viathe hydraulic passage 59 b in accordance with a cylinder deactivationsignal, both of the pin 57 a and the disengaging pin 57 b slide towardthe valve operating rocker arm 55 b against the biasing force of the pinspring 58, and the interface between the pin 57 a and the disengagingpin 57 b corresponds to the interface between the cam lifting rocker arm54 b and the valve operating rocker arm 55 b to disconnect these rockerarms 54 b and 55 b, as shown in FIG. 9B. The intake valve side is alsoconstructed in a similar manner. The hydraulic passages 59 a and 59 bare connected to an oil pump 70 via the spool valve 71 which is providedfor ensuring hydraulic pressure of the variable valve timing mechanismVT.

As shown in FIG. 10, a passage for deactivation 72 branching from thespool valve 71 is connected to the hydraulic passage 59 b in the rockerarm shaft 62, and a passage for canceling deactivation 73 branching fromthe spool valve 71 is connected to the hydraulic passage 59 a. The POILsensor S5 is connected to the passage for canceling deactivation 73. ThePOIL sensor S5 monitors hydraulic pressure in the passage for cancelingdeactivation 73, which exhibits low values during a deactivationoperation and exhibits high values during normal operation. The TOILsensor S6 (shown in FIG. 1) is connected to an oil supplying passage 74which branches from a passage connecting the outlet of the oil pump 70and the spool valve 71 and which supplies operating oil to the engine Eso as to monitor the temperature of the operating oil.

When the condition for entering into a cylinder deactivation operation,which will be described below, is satisfied, the spool valve 71 isoperated in accordance with a signal from the FIECU 11, and hydraulicpressure is applied to the hydraulic chamber 56 via the oil pump 70 andthe hydraulic passage 59 b in both the intake valve and exhaust valvesides. Subsequently, the pins 57 a, which have been bridging the camlifting rocker arms 54 a, 54 b and the valve operating rocker arms 55 a,55 b together with the disengaging pin 57 b, slide toward the valveoperating rocker arms 55 a, 55 b, and the cam lifting rocker arms 54 a,54 b and the valve operating rocker arms 55 a, 55 b are disconnected.

In this state, although the cam lifting rocker arms 54 a and 54 b aredriven by the rotating lift cam 52, the movements are not transmitted tothe valve operating rocker arms 55 a and 55 b which have beendisconnected from the cam lifting rocker arms 54 a and 54 b. As aresult, because the valve operating rocker arms 55 a and 55 b are notdriven and the intake valve IV and the respective ports of the exhaustvalve EV remain closed, a cylinder deactivation operation of the enginecan be performed.

Operation for Switching into Cylinder Deactivation Operation

Now, the operation for switching into a cylinder deactivation operationwill be explained with reference to FIG. 2.

The term “cylinder deactivation operation” herein means an engineoperation state in which both of the intake and exhaust valves remain intheir closing positions by means of the variable valve timing mechanismVT under predetermined conditions during regenerative deceleration, andit is performed in order to reduce engine friction and to increase theenergy regenerated during deceleration. In the flowchart shown in FIG.2, a flag (i.e., cylinder deactivation executing flag F_ALCS included ina deactivation determining section) used to alternate the engineoperation state between a cylinder deactivation operation and normaloperation in which all cylinders are active is set and reset at apredetermined period.

In step S100A, it is determined whether the value of a flag F_GDECCS(included in a deceleration state determining section) is “1”. The flagF_GDECCS is provided since cancellation of the cylinder deactivationoperation is required when the degree of deceleration is relativelygreat. When the result of the determination in step S100A is “YES”, theoperation proceeds to step S114, and when the result is “NO”, theoperation proceeds to step S100B.

In step S100B, it is determined whether the value of a flag F_GDECMA(included in the deceleration state determining section) is “1”. Theflag F_GDECMA is provided since cancellation of regenerativedeceleration is required when the degree of deceleration is relativelygreat. When the result of the determination in step S100A is “YES”, theoperation proceeds to step S114, and when the result is “NO”, theoperation proceeds to step S101. The reason for providing thedetermination in step S100A is that it is better not to execute thecylinder deactivation operation when stopping of the vehicle has thehighest priority.

When a braking operation of high deceleration is applied, negativepressure in the master vac is greatly reduced (i.e., the absolutepressure is increased), and subsequently, there is a high possibilitythat the engine operation state may return to normal operation from thecylinder deactivation operation with a high possibility (the logic willbe discussed below in relation to step S160); therefore, the cylinderdeactivation operation should be cancelled during high decelerationtraveling.

The reason for providing the determination in step S100B is that it isbetter not to execute the cylinder deactivation operation in order toprotect the battery from a rapidly increased regenerative electricenergy during high deceleration traveling. The flag F_GDECCS and theflag F_GDECMA are flags which are set to be “1” when the degree ofdeceleration is equal to or greater than a predetermined value (forexample, 0.3×9.8 m/s²). The degree of deceleration is calculated basedon a fluctuation of engine revolution NE and a fluctuation of vehiclespeed measured by wheel speed sensors. Steps S100A and S100B constitutethe deceleration state determining section. The degree of decelerationmay be measured by an accelerometer (not shown).

In step S101, it is determined whether designated fail-safe signals havebeen detected. When the result of the determination in step S101 is“NO”, the operation proceeds to step S102, and when the result is “YES”,the operation proceeds to step S114. The operation should proceed inthis way because it is better not to execute the cylinder deactivationoperation when the engine has some abnormalities.

In step S102, it is determined whether a flag F_ALCSSOL is “1”. When theflag F_ALCSSOL is “1”, it means that the solenoid for a cylinderdeactivation operation in the spool valve 71 is ON. When the result ofthe determination in step S102 is “YES”, the operation proceeds to stepS105, and when the result is “NO”, the operation proceeds to step S103.In step S103, as will be explained below, it is determined whether thepre-deactivation conditions permitting the cylinder deactivationoperation are satisfied (F_ALCSSTB_JUD); then, the operation proceeds tostep S104. The cylinder deactivation operation is executed only when thepre-deactivation conditions are satisfied in step S103.

In step S104, it is determined whether the value of a cylinderdeactivation stand-by flag F_ALCSSTB is “1”. The flag F_ALCSSTB is setto be “1” when the pre-deactivation conditions are satisfied in stepS103, and is set to be “0” when the pre-deactivation conditions are notsatisfied. According to the flag F_ALCSSTB, it is determined whether ornot a cylinder deactivation operation may be executed in accordance withthe operation state of the vehicle. When the result of the determinationin step S1104 is “YES”, which means that the pre-deactivation conditionsare satisfied, the operation proceeds to step S105, and when the resultis “NO”, which means that the pre-deactivation conditions are notsatisfied, the operation proceeds to step S114.

In step S105, as will be explained below, it is determined whether thedeactivation cancellation conditions are satisfied (F_ALCSSTP JUD);then, the operation proceeds to step S106. When the deactivationcancellation conditions are satisfied in step S105, the cylinderdeactivation operation will not be executed. In contrast to the judgmenton the pre-deactivation conditions, the judgment on the deactivationcancellation conditions is always performed (continuously monitored),when the operation shown in FIG. 2 is executed.

In step S106, it is determined whether the value of a deactivationcancellation flag F_ALCSSTP is “1”. The deactivation cancellation flagF_ALCSSTP (included in the deactivation cancellation determiningsection) is set to be “1” when the deactivation cancellation conditionsare satisfied in step S105, and is set to be “0” when the deactivationcancellation conditions are not satisfied. According to the flagF_ALCSSTP, it is determined whether or not the cylinder deactivationoperation may be cancelled in accordance with the operation state of thevehicle during the cylinder deactivation operation of the engine. Whenthe result of the determination in step S106 is “YES”, which means thatthe cancellation conditions are satisfied, the operation proceeds tostep S114, and when the result is “NO”, which means that thecancellation conditions are not satisfied, the operation proceeds tostep S107.

In step S107, it is determined whether the value of a solenoid ON delaytimer TALCSDL1, as will be explained below, is “0”. When the result ofthe determination in step S107 is “YES”, which means that apredetermined period has passed, the operation proceeds to step S108,and when the result is “NO”, which means that a predetermined period hasnot passed, the operation proceeds to step S116.

In step S108, a predetermined value #TMALCS2 is set in a solenoid OFFdelay timer TALCSDL2 for the spool valve 71, then the operation proceedsto step S109. This procedure is performed in order to ensure a certainperiod of time has passed from completion of the determination in stepS105 to completion of the OFF operation of the solenoid for the spoolvalve 71 in step S116, which will be explained below, when the engineoperation is alternated from the cylinder deactivation operation tonormal operation.

In step S109, the flag F_ALCSSOL of the solenoid for the cylinderdeactivation operation is set to “1”, i.e., the solenoid for thecylinder deactivation operation in the spool valve 71 is set to be ON,then the operation proceeds to step S110.

In step S110, it is determined by the POIL sensor S5 whether hydraulicpressure is actually produced after the solenoid for the cylinderdeactivation operation was set to be ON. Specifically, it is determinedwhether or not engine oil pressure POIL is equal to or greater thancylinder deactivation permissible oil pressure #POILCSH (e.g., 137 kPa(=1.4 kg/cm²)). When the result of the determination in step S110 is“YES”, which means that engine oil pressure POIL is at the high pressureside, the operation proceeds to step S111, and when the result is “NO”(there is hysteresis), the operation proceeds to step S118. An oilpressure switch may be provided for the determination instead of thePOIL sensor S5.

In step S111, it is determined whether the value of a cylinderdeactivation execution delay timer TCSDLY1 is “0” in order to ensure acertain period of time has passed from when the spool valve 71 isswitched on to when oil pressure is produced. When the result of thedetermination in step S111 is “YES”, the operation proceeds to stepS112, and when the result is “NO”, the operation proceeds to step S120A.

In step S112, a timer value #TMNCSDL2, which is retrieved from a tabledepending on the engine running speed NE, is set in a cylinderdeactivation cancellation delay timer TCSDLY2. The reason for settingthe timer value #TMNCSDL2 depending on the engine running speed NE isthat the oil pressure response changes depending on the engine runningspeed NE. Therefore, the lower the engine running speed NE is, thegreater the timer value #TMNCSDL2 is.

In step S113, the cylinder deactivation executing flag F_ALCS is set to“1”, and the control operation of this flow is terminated.

In step S114, it is determined whether the value of the solenoid OFFdelay timer TALCSDL2 is “0”. When the result of the determination instep S114 is “YES”, which means that a predetermined period has passed,the operation proceeds to step S115, and when the result is “NO”, whichmeans that a predetermined period has not passed, the operation proceedsto step S109.

In step S115, a predetermined value #TMALCS 1 is set in the solenoid ONdelay timer TALCSDL1 for the spool valve 71, then the operation proceedsto step S116. This procedure is performed in order to ensure a certainperiod of time has passed from completion of the determination in stepS105 to an ON operation of the solenoid for the spool valve 71 in stepS109 when the engine operation is alternated from the cylinderdeactivation operation to normal operation.

In step S116, the flag F_ALCSSOL of the solenoid for the cylinderdeactivation operation is set to “0”, i.e., the solenoid for thecylinder deactivation operation in the spool valve 71 is set to be OFF,then the operation proceeds to step S117.

In step S117, it is determined by the POIL sensor S5 whether hydraulicpressure is actually reduced after the solenoid for the cylinderdeactivation operation was set to be OFF. Specifically, it is determinedwhether or not engine oil pressure POIL is equal to or less thancylinder deactivation cancellation oil pressure #POILCSL (e.g., 98 kPa(=1.0 kg/cm²)). When the result of the determination in step S117 is“YES”, which means that engine oil pressure POIL is at the low pressureside, the operation proceeds to step S118, and when the result is “NO”(there is hysteresis), the operation proceeds to step S111. An oilpressure switch may be provided for the determination instead of thePOIL sensor S5.

In step S118, it is determined whether the value of the cylinderdeactivation cancellation delay timer TCSDLY2 is “0” in order to ensurea certain period of time has passed from when the spool valve 71 isswitched off to when oil pressure is reduced. When the result of thedetermination in step S118 is “YES”, the operation proceeds to stepS119, and when the result is “NO”, the operation proceeds to step S113.

In step S119, a timer value #TMNCSDL1, which is retrieved from a tabledepending on an engine running speed NE, is set in the cylinderdeactivation execution delay timer TCSDLY1, then the operation proceedsto step S120A. The reason for setting the timer value #TMNCSDL1depending on the engine running speed NE is that the oil pressureresponse changes depending on the engine running speed NE. Therefore,the lower the engine running speed NE is, the greater the timer value#TMNCSDL1 is.

In step S120A, a timer value #TMCSCEND (e.g., 30 seconds) is set in acylinder deactivation compulsory cancellation timer TCSCEND, then theoperation proceeds to step S120. The cylinder deactivation compulsorycancellation timer TCSCEND is provided to compulsorily cancel thecylinder deactivation operation when a predetermined period has passedsince the beginning of the cylinder deactivation operation.

In step S120, the cylinder deactivation executing flag F_ALCS is set to“0”, and the control operation of this flow is terminated.

Operation for Determining Whether the Pre-Deactivation ConditionsPermitting the Cylinder Deactivation Operation are Satisfied

Next, the operation for determining whether the pre-deactivationconditions permitting the cylinder deactivation operation are satisfiedin step S103 shown in FIG. 2 will be explained with reference to FIG. 3.This operation will be repeated at a predetermined period.

In step S131, it is determined whether ambient temperature TA is withina predetermined range, i.e., whether the ambient temperature TAsatisfies the following inequality:

lowest permissible ambient temperature for cylinder deactivation#TAALCSL (e.g. 0° C.) ≦TA≦highest permissible ambient temperature forcylinder deactivation #TAALCSH (e.g., 50° C.). When it is determined, instep S131, that the ambient temperature TA is within the predeterminedrange, the operation proceeds to step S132. When it is determined thatthe ambient temperature TA is out of the predetermined range, theoperation proceeds to step S144. This procedure is provided because thecylinder deactivation operation may make the engine unstable whenambient temperature TA is below the lowest permissible ambienttemperature for cylinder deactivation #TAALCSL or when the ambienttemperature TA is above the highest permissible ambient temperature forcylinder deactivation #TAALCSH.

In step S132, it is determined whether cooling water temperature TW iswithin a predetermined range, i.e., whether cooling water temperature TWsatisfies the following inequality:

lowest permissible cooling water temperature for cylinder deactivation#TWALCSL (e.g., 70° C.)≦TA≦highest permissible cooling water temperaturefor cylinder deactivation #TWALCSH (e.g., 100° C.). When it isdetermined, in step S132, that the cooling water temperature TW iswithin the predetermined range, the operation proceeds to step S133.When it is determined that the cooling water temperature TW is out ofthe predetermined range, the operation proceeds to step S144. Thisprocedure is provided because the cylinder deactivation operation maymake the engine unstable when cooling water temperature TW is below thelowest permissible cooling water temperature for cylinder deactivation#TWALCSL or when the cooling water temperature TW is above the highestpermissible cooling water temperature for cylinder deactivation#TWALCSH.

In step S133, it is determined whether ambient pressure PA is equal toor greater than a lowest permissible ambient pressure for cylinderdeactivation #PAALCS (e.g., 77.3 kPa (=580 mmHg)). When the result ofthe determination in step S133 is “YES”, which means that the ambientpressure PA is equal to or greater than the lowest permissible ambientpressure #PAALCS, the operation proceeds to step S134, and when theresult is “NO”, the operation proceeds to step S144. This procedure isprovided because it is undesirable to execute the cylinder deactivationoperation when the ambient pressure is relatively low. For example, whenthe cylinder deactivation operation is executed under such a condition,negative pressure in the master vac for the brake system may not beensured to be sufficient for the braking operation.

In step S134, it is determined whether voltage VB of the 12-voltauxiliary battery 4 (power supply voltage) is equal to or greater than alowest permissible voltage for cylinder deactivation #VBALCS (e.g., 10.5V). When the result of the determination in step S134 is “YES”, whichmeans that the voltage VB is equal to or greater than the lowestpermissible voltage #VBALCS, the operation proceeds to step S135, andwhen the result is “NO”, the operation proceeds to step S144. Thisprocedure is provided because the response of the spool valve 71 isdegraded when the voltage VB of the 12-volt auxiliary battery 4 isrelatively low. In addition, this procedure is provided in order toprotect the auxiliary battery 4 when the voltage thereof is decreasedunder a low ambient temperature or when the auxiliary battery 4 isdeteriorated.

In step S135, it is determined whether battery temperature TBAT of thebattery 3 is equal to or lower than a highest permissible batterytemperature for cylinder deactivation #TBALCSH (e.g., 40° C.). When theresult of the determination in step S135 is “YES”, the operationproceeds to step S136, and when the result is “NO”, the operationproceeds to step S144.

In step S136, it is determined whether the battery temperature TBAT ofthe battery 3 is equal to or greater than a lowest permissible batterytemperature for cylinder deactivation #TBALCSL (e.g., 10° C.). When theresult of the determination in step S136 is “YES”, the operationproceeds to step S137, and when the result is “NO”, the operationproceeds to step S144. Steps 135 and 136 are provided because it isundesirable to execute the cylinder deactivation operation when thetemperature of the battery 3 is out of the predetermined range.

In step S137, it is determined whether a fuel cut-off duringdeceleration is being executed according to whether a fuel cut-offflagF_FC is “1”. When the result of the determination in step S137 is “YES”,the operation proceeds to step S138, and when the result is “NO”, theoperation proceeds to step S144. This procedure is provided because thefuel supply must be stopped prior to execution of the cylinderdeactivation operation.

In step S138, it is determined whether oil temperature TOIL is within apredetermined range, i.e., whether oil temperature the TOIL satisfiesthe following inequality:

lowest permissible oil temperature for cylinder deactivation #TOALCSL(e.g., 70° C.)≦TOIL≦highest permissible oil temperature for cylinderdeactivation #TOALCSH (e.g., 100° C.). When it is determined, in stepS138, that the oil temperature TOIL is within the predetermined range,the operation proceeds to step S139. When it is determined that oiltemperature TOIL is out of the predetermined range, the operationproceeds to step S144. This procedure is provided because the responsein alternation between normal operation and the cylinder deactivationoperation of the engine may be unstable if the cylinder deactivationoperation is executed when the oil temperature TOIL is below the lowestpermissible oil temperature for cylinder deactivation #TOALCSL or whenthe oil temperature TOIL is above the highest permissible oiltemperature for cylinder deactivation #TOALCSH.

In step S139, it is determined whether the value of the cylinderdeactivation stand-by flag F_ALCSSTB is “1”, which is set through theoperation shown in FIG. 3. When the result of the determination in stepS139 is “YES”, the operation proceeds to step S142, and when the resultis “NO”, the operation proceeds to step S140.

In step S140, it is determined whether intake negative pressure PBGA inthe intake passage, i.e., intake air pressure, is higher (i.e., closerto atmospheric pressure) than a permissible negative pressure forcylinder deactivation #PBGALCS (i.e., the first predeterminedthreshold). The permissible negative pressure for cylinder deactivation#PBGALCS is retrieved from a table which was defined in accordance withthe engine running speed NE such that the greater the engine runningspeed NE is, the less (closer to vacuum) the permissible negativepressure #PBGALCS is. For example, the permissible negative pressure#PBGALCS may be set to be −80 kPa (=−600 mmHg) at an engine runningspeed NE of 3000 rpm.

This procedure is provided in order not to immediately execute thecylinder deactivation operation, but to execute the operation afterutilizing the intake negative pressure for ensuring negative pressure inthe master vac when the load of the engine is considerably great, i.e.,the intake negative pressure is lower (closer to vacuum) than thepermissible negative pressure #PBGALCS. When the result of thedetermination in step S140 is “YES” (i.e., low load and small negativepressure), the operation proceeds to step S141, and when the result is“NO” (i.e., high load and large negative pressure), the operationproceeds to step S143. In step S143, a flag F_DECPBUP is set to “1”,then the operation proceeds to step S145. The flag F_DECPBUP is used toclose or open the secondary air passage.

In step S140, the determination may be made based on master vac negativepressure MPGA instead of the intake negative pressure PBGA. In thiscase, when the master vac negative pressure MPGA is lower than apermissible negative pressure for continuation of cylinder deactivation#MPALCS (i.e., the second predetermined threshold), the flag F_DECPBUPis set to “1” in step S143, then the operation proceeds to step S145.This procedure corresponds to the second embodiment of the presentinvention.

In step S141, the flag F_DECPBUP is set to “0”, then the operationproceeds to step S142. In step S142, the cylinder deactivation stand-byflag F_ALCSSTB is set to “1” because pre-deactivation conditions aresatisfied, and the control operation of this flow is terminated.

On the other hand, in step S144, the flag F_DECPBUP is set to “0”, thenthe operation proceeds to step S145. In step S145, the cylinderdeactivation stand-by flag F_ALCSSTB is set to “0” becausepre-deactivation conditions are not satisfied, and the control operationof this flow is terminated.

When the value of the flag F_DECPBUP is “1”, the secondary air passage33 is closed under a certain condition, and when the value of the flagF_DECPBUP is “0”, the secondary air passage 33 is opened under a certaincondition.

In other words, when it is determined that the engine is under a highload condition, the secondary air passage 33 is closed (step S143), thecylinder deactivation operation is not started (step S145), and thecontrol operation is restarted from step S131. When it is determined, instep S140, that the intake negative pressure PBGA becomes apredetermined value, the control operation is triggered to proceed tosteps S141 and S142, then the pre-deactivation conditions are deemed tobe satisfied, i.e., the cylinder deactivation stand-by flag F_ALCSSTB isset to “1”.

Accordingly, the cylinder deactivation operation is executed afterensuring negative pressure in the master vac to be sufficient by closingthe secondary air passage 33 at the beginning of deceleration traveling.Because pressure in the master vac is sufficiently low, the brakingforce is sufficiently assisted even when negative pressure in the mastervac is reduced by the braking operation. Furthermore, fuel consumptionis greatly improved because the cylinder deactivation operation is lessfrequently cancelled and regenerative energy is fully utilized.

Operation for Determining Whether the Deactivation CancellationConditions are Satisfied

Next, the operation for determining whether the deactivationcancellation conditions shown in step S105 in FIG. 2 are satisfied willbe explained with reference to FIG. 4. This operation will be repeatedat a predetermined period.

In step S151, it is determined whether the value of the cylinderdeactivation compulsory cancellation timer TCSCEND is “0”. When theresult of the determination in step S151 is “YES”, the operationproceeds to step S169, and when the result is “NO”, the operationproceeds to step S152, because the cylinder deactivation operationshould be cancelled when the value of the cylinder deactivationcompulsory cancellation timer TCSCEND is “0”.

In step S152, it is determined whether the value of the fuel cut-offflagF_FC is “1”. When the result of the determination in step S152 is “YES”,the operation proceeds to step S153, and when the result is “NO”, theoperation proceeds to step S166. This procedure is provided because thepurpose of the cylinder deactivation operation is to further obtainregenerative energy equivalent to the reduction in engine frictionresulting when the fuel supply is stopped during deceleration traveling.

In step S166, a cylinder deactivation ending flag F_ALCSEND is set to“0”, then the operation proceeds to step S169.

In step S153, it is determined whether the value of the cylinderdeactivation ending flag F_ALCSEND is “1”. When the result of thedetermination in step S153 is “YES”, the operation proceeds to stepS169, and when the result is “NO”, the operation proceeds to step S154.

In step S154, it is determined whether deceleration regeneration isbeing performed. When the result of the determination in step S154 is“YES”, the operation proceeds to step S155, and when the result is “NO”,the operation proceeds to step S169.

In step S155, it is determined whether the value of an MT/CVT indicationflag F_AT is “1”. When the result of the determination in step S155 is“NO”, which means that the present vehicle employs an MT (manualtransmission), the operation proceeds to step S156, and when the resultis “YES”, which means that the present vehicle employs an AT (automatictransmission) or a CVT, the operation proceeds to step S167.

In step S167, it is determined whether the value of an in-gearindication flag F_ATNP is “1”. When the result of the determination instep S167 is “NO”, which means that the vehicle is in driving mode, theoperation proceeds to step S168, and when the result is “YES”, whichmeans that the transmission is in N (neutral) or P (parking) position,the operation proceeds to step S169.

In step S168, it is determined whether the value of a reverse positionindication flag F_ATPR is “1”. When the result of the determination instep S168 is “YES”, which means that the transmission is in reverseposition, the operation proceeds to step S169, and when the result is“NO”, which means that the transmission is in a position other than thereverse position, the operation proceeds to step S158.

Through the procedures in steps S167 and S168, the cylinder deactivationoperation is cancelled in N/P or reverse position.

In step S156, it is determined whether the previous gear position NGR isequal to or higher than a lowest permissible gear position for cylinderdeactivation #NGRALCS (e.g., third gear). When the result of thedetermination in step S156 is “YES”, i.e., higher gear position, theoperation proceeds to step S157, and when the result is “NO”, i.e.,lower gear position, the operation proceeds to step S169. This procedureis provided because the regeneration efficiency is reduced in low gearpositions, and to avoid a frequent alternation into the cylinderdeactivation operation when the vehicle is in a traffic jam.

In step S157, it is determined whether the value of a half-engagedclutch indication flag F_NGRHCL is “1”. When the result of thedetermination in step S157 is “YES”, which indicates a half-engagedclutch state, the operation proceeds to step S169, and when the resultis “NO”, the operation proceeds to step S158. By providing thisprocedure, it is possible to avoid undesirable cylinder deactivationoperations which may cause an engine stall when the clutch is placed ina half-engaged state to stop the vehicle, or an insufficientacceleration performance the clutch is placed in a half-engaged statefor gear position shifting to accelerate the vehicle.

In step S158, it is determined whether an engine revolution decreaseamount DNE is equal to or greater than a highest permissible enginerevolution decrease amount for cylinder deactivation #DNEALCS (e.g., 100rpm). When the result of the determination in step S158 is “YES”, whichmeans that the engine revolution is considerably decreased, theoperation proceeds to step S169, and when the result is “NO”, theoperation proceeds to step S159. This procedure is provided to avoidundesirable cylinder deactivation operations which may cause an enginestall when the engine revolution is rapidly decreasing.

In step S159, it is determined whether a vehicle speed VP is within apredetermined range, i.e., whether the vehicle speed VP satisfies thefollowing inequality:

lowest permissible vehicle speed for continuation of cylinderdeactivation #VPALCSL (e.g., 10 km/h)≦VP≦highest permissible vehiclespeed for continuation of cylinder deactivation #VPALCSH (e.g., 60km/h). When it is determined, in step S159, that the vehicle speed VP iswithin the predetermined range, the operation proceeds to step S160.When it is determined that the vehicle speed VP is out of thepredetermined range, the operation proceeds to step S169. Accordingly,the cylinder deactivation operation is cancelled when the vehicle speedVP is below the lowest permissible vehicle speed for cylinderdeactivation continuation #VPALCSL or when the vehicle speed VP is abovethe highest permissible vehicle speed for cylinder deactivationcontinuation #VPALCSH.

In step S160, it is determined whether the master vac negative pressureMPGA is equal to or lower than (closer to vacuum) the permissiblenegative pressure for continuation of cylinder deactivation #MPALCS(i.e., the second predetermined threshold). The permissible negativepressure for continuation of cylinder deactivation #MPALCS is retrievedfrom a table which was defined depending on the vehicle speeds VP suchthat the greater the vehicle speed VP is, the lower (closer to vacuum)the permissible negative pressure #MPALCS is. The permissible negativepressure #MPALCS is preferably determined in accordance with the kineticenergy of the vehicle, i.e., the vehicle speed due to the use of themaster vac negative pressure MPGA to stop the vehicle. For example, thepermissible negative pressure #MPALCS may be set to be −60 kPa (=450mmHg) at a vehicle speed VP of 40 km/h.

In step S160, when the master vac negative pressure MPGA is lower thanthe permissible negative pressure for continuation of cylinderdeactivation #MPALCS, which means that the master vac negative pressureMPGA is closer to vacuum, the operation proceeds to step S161. When themaster vac negative pressure MPGA is higher than the permissiblenegative pressure for continuation of cylinder deactivation #MPALCS,which means that the master vac negative pressure MPGA is closer toatmospheric pressure, the operation proceeds to step S169. Thisprocedure is provided because it is undesirable to continue the cylinderdeactivation operation when the master vac negative pressure MPGA is notsufficiently low.

In step S161, it is determined whether a remaining battery charge QBATis within a predetermined range, i.e., whether the remaining batterycharge QBAT satisfies the following inequality:

lowest permissible remaining battery charge for continuation of cylinderdeactivation #QBALCSL (e.g., 30%)≦QBAT≦highest permissible remainingbattery charge for continuation of cylinder deactivation #QBALCSH (e.g.,80%). When it is determined, in step S161, that the remaining batterycharge QBAT is within the predetermined range, the operation proceeds tostep S162. When it is determined that the remaining battery charge QBATis out of the predetermined range, the operation proceeds to step S1169.Accordingly, the cylinder deactivation operation is cancelled when theremaining battery charge QBAT is below the lowest permissible remainingbattery charge for cylinder deactivation continuation #QBALCSL or whenthe remaining battery charge QBAT is above the highest permissibleremaining battery charge for cylinder deactivation continuation#QBALCSH. This procedure is provided because electric energy supplied tothe motor M for assisting the engine driving cannot be ensured when theremaining battery charge QBAT is too low, and because regenerativeenergy cannot be drawn when the remaining battery charge QBAT is toohigh.

In step S162, it is determined whether the engine running speed NE iswithin a predetermined range, i.e., whether the engine running speed NEsatisfies the following inequality:

lowest permissible engine running speed for continuation of cylinderdeactivation #NALCSL (e.g., 800 rpm)≦NE≦highest permissible enginerunning speed for continuation of cylinder deactivation #NALCSH (e.g.,3000 rpm). When it is determined, in step S162, that the engine runningspeed NE is within the predetermined range, the operation proceeds tostep S163. When it is determined that the engine running speed NE is outof the predetermined range, the operation proceeds to step S169.Accordingly, the cylinder deactivation operation is cancelled when theengine running speed NE is below the lowest permissible engine runningspeed for cylinder deactivation continuation #NALCSL or when the enginerunning speed is above the highest permissible engine running speed forcylinder deactivation continuation #NALCSH. This procedure is providedbecause the regenerative efficiency may be low or hydraulic pressure foralternating into the cylinder deactivation operation may not be ensuredwhen the engine running speed NE is too low, and because the operationoil for executing a cylinder deactivation operation may be excessivelyconsumed when the engine running speed NE is too high.

In step S163, it is determined whether the value of an idling indicationflag F_THIDLMG is “1”. When the result of the determination in step S162is “YES”, which means that the throttle of the engine is not completelyclosed, the operation proceeds to step S169, and when the result is“NO”, which means that the throttle of the engine is completely closed,the operation proceeds to step S164. This procedure is provided tocancel the cylinder deactivation operation even when the throttle isslightly opened from a completely closed state so that marketability ofthe vehicle is enhanced.

In step S164, it is determined whether the engine oil pressure POIL isequal to or greater than a lowest permissible oil pressure forcontinuation of cylinder deactivation #POALCS (e.g., with a hysteresisrange from 98 to 137 kPa (from 1.0 to 1.4 kg/cm²)). When the result ofthe determination in step S162 is “YES”, the operation proceeds to stepS165, and when the result is “NO”, the operation proceeds to step S169.This procedure is provided because hydraulic pressure for executing thecylinder deactivation operation (e.g., hydraulic pressure for operatingthe spool valve 71) cannot be ensured when the engine oil pressure POILis less than the lowest permissible oil pressure for continuation ofcylinder deactivation #POALCS.

In step S165, the conditions for canceling the cylinder deactivationoperation are not satisfied; therefore, the deactivation cancellationflag F_ALCSSTP is set to “0” so as to continue the cylinder deactivationoperation, and the control operation of this flow is terminated.

In step S169, it is determined whether the value of the deactivationcancellation flag F_ALCSSTP indicating the result of the operation inthis flowchart is “0”. When the result of the determination in step S169is “YES”, the operation proceeds to step S170, and when the result is“NO”, the operation proceeds to step S171.

In step S170, the cylinder deactivation ending flag F_ALCSEND is set to“1”, then the operation proceeds to step S171. In step S171, theconditions for canceling the cylinder deactivation operation aresatisfied; therefore, the deactivation cancellation flag F_ALCSSTP isset to “1”, and the control operation of this flow is terminated.

The cylinder deactivation ending flag F_ALCSEND is provided so as not tocancel the cylinder deactivation operation unless deceleration fuelcut-off is ended and the engine returns to a normal operation state,i.e., to avoid hunting in control.

Operation for Selecting Air Control Mode

Next, the operation for selecting air control mode will be explainedwith reference to FIGS. 5 and 6. The purpose of this control operationis to appropriately open/close the control valve 34 of the secondary airpassage 33 in accordance with the engine running state. This operationwill be repeated at a predetermined period.

In step S201, it is determined whether the engine is in starting modeaccording to whether the value of a starting mode flag F_STMOD is “1”.When the result of the determination in step S201 is “YES”, theoperation proceeds to step S205, and when the result is “NO”, theoperation proceeds to step S202.

In step S205, a feedback flag F_FB is set to “0”, and in step S206, theengine operation state is deemed to be in starting mode in which acertain amount of air is ensured, then, the control operation of thisflow is terminated. When the feedback flag F_FB is “0”, the openingdegree of the control valve 34 is not controlled in a feedback manner.

In step S202, it is determined whether the throttle is in a widelyopened state according to whether the value of a throttle opening flagF_THIDLE is “1”. When the result of the determination in step S202 is“YES”, which means that the throttle is in a widely opened state, theoperation proceeds to step S221, and when the result is “NO”, theoperation proceeds to step S203.

In step S203, it is determined whether the value of the fuel cut-offflag F_FC is “1”. When the result of the determination in step S203 is“YES”, the operation proceeds to step S216, and when the result is “NO”,the operation proceeds to step S204.

In step S204, it is determined whether the vehicle speed VP is greaterthan a predetermined threshold #VAIC. When the result of thedetermination in step S204 is “YES”, which means that the vehicle istraveling at a high speed, the operation proceeds to step S207, and whenthe result is “NO”, the operation proceeds to step S211. In step S207,the feedback flag F_FB is set to “0”, and the control operation of thisflow is terminated.

In step S211, it is determined whether the value of the MT/CVTindication flag F_AT is “1”. When the result of the determination instep S211 is “NO”, which means that the present vehicle employs an MT(manual transmission), the operation proceeds to step S213, and when theresult is “YES”, which means that the present vehicle employs an AT(automatic transmission) or a CVT, the operation proceeds to step S212.

In step S212, it is determined whether the value of the in-gearindication flag F_ATNP is “1”. When the result of the determination instep S212 is “NO”, which means that the vehicle is in driving mode, theoperation proceeds to step S208, and when the result is “YES”, whichmeans that the transmission is in N (neutral) or P (parking) position,the operation proceeds to step S213.

In step S208, it is determined whether the value of a flag F_IAT is “1”.The flag FIAT is provided to indicate that feedback of number of enginerevolution at idling is prohibited during an in-gear state. When theresult of the determination in step S208 is “YES”, which means that theengine is in in-gear open loop control mode for idling, the operationproceeds to step S209, and when the result is “NO”, the operationproceeds to step S213. In step S209, the feedback flag F_FB is set to“0”, and in step S210, the engine operation state is deemed to be in “ATOPEN” mode in which a certain amount of air is ensured to maintaincreeping, then, the control operation of this flow is terminated.

In step S213, the feedback flag F_FB is set to “1”, in step S214, afeedback amount IFB is calculated, and in step S215, the engineoperation state is deemed to be in “FEEDBACK” mode, then, the controloperation of this flow is terminated.

In step S216, the feedback flag F_FB is set to “0”, and in step S217, itis determined whether the value of the flag F_DECPBUP is “1”. The flagF_DECPBUP is set or reset in steps S143 and S141 as shown in FIG. 3.When the result of the determination in step S217 is “YES”, theoperation proceeds to step S224, and when the result is “NO”, theoperation proceeds to step S218. The control valve 34 is closed(corresponding to step S224 in FIG. 6) when the cylinder deactivationoperation is not allowed (corresponding to steps S143 and S145, and stepS217 in FIG. 5).

In step S218, a secondary air correction amount during deceleration IDECis calculated, then, the operation proceeds to step S219.

In step S219, it is determined whether the secondary air correctionamount IDEC is “0”. When the result of the determination in step S219 is“YES”, which means that there is no correction amount (i.e., IDEC=0),the control operation of this flow is terminated, and when the result is“NO”, which means that there is some correction amount (i.e., IDEC≠0),the operation proceeds to step S220.

In step S221, the feedback flag F_FB is set to “0”. In step S222, it isdetermined whether the engine revolution speed NE is greater than athreshold #NE which is used for the determination of entering into adeactivation mode. When the result of the determination in step S222 is“YES”, which means that the engine revolution speed is relatively high,the operation proceeds to step S224, and when the result is “NO”, whichmeans that the engine revolution speed is relatively low, the controloperation of this flow is terminated. In step S224, because pressure inthe intake passage becomes closer to atmospheric pressure, the engine iscontrolled to enter into a deactivation mode in which the control valve34 is closed so that negative pressure is generated in the intakepassage, then, the control operation of this flow is terminated.

Accordingly, in this embodiment, it is included in the control operationthat the operator of the vehicle intends to stop the vehicle when thevehicle experiences deceleration by a braking operation of the operatorand the degree of deceleration is greater than 0.3 G (0.3×9.8 m/s²), thevehicle can quickly stop in accordance with the operator's desirewithout entering into the cylinder deactivation operation.

On the other hand, when the vehicle is moderately decelerating, thedetermination of a cylinder deactivation, i.e., the operation fordetermining whether the pre-deactivation conditions permitting thecylinder deactivation operation are satisfied, as shown in FIG. 2, isperformed. In this process, when the intake negative pressure PBGA inthe intake passage is lower (i.e., closer to vacuum) than thepermissible negative pressure for cylinder deactivation #PBGALCS, thesecondary air passage 33 is prepared to be closed (step S143 shown inFIG. 3) in order to efficiently utilize negative pressure in the intakepassage for ensuring negative pressure in the master vac, and thecylinder deactivation operation is not executed (step S145 shown in FIG.3 and step S120 shown in FIG. 2).

Upon completion of preparation, the secondary air passage 33 is closedby the control valve 34. Accordingly, negative pressure in the mastervac is efficiently ensured by utilizing negative pressure in the intakepassage. When negative pressure in the master vac is ensured andpressure in the intake passage (intake pressure) is increased, thecontrol operation is triggered by this intake pressure (step S140 shownin FIG. 3), the control valve 34 is closed (step S141 shown in FIG. 3),and the cylinder deactivation operation is executed (step S142 shown inFIG. 3 and step S113 shown in FIG. 2). When the cylinder deactivationoperation is cancelled through the determination of whether thedeactivation cancellation conditions are satisfied (shown in FIG. 4 andstep S105 shown in FIG. 2), the engine enters into normal operation(step S120 shown in FIG. 2). Accordingly, negative pressure in themaster vac which is influenced by the cylinder deactivation operationcan be ensured so as to maintain the brake performance while enabling agreat improvement in the fuel consumption of the vehicle due to thecylinder deactivation operation.

As explained above, in this embodiment, it is possible to maintainnegative pressure in the master vac at low pressure side (closer tovacuum); therefore, negative pressure in the master vac is efficientlyutilized for ensuring the assist force for the braking force so that thebraking effort of the operator is reduced.

In addition, because the permissible negative pressure for cylinderdeactivation #PBGALCS as a threshold for the intake negative pressurePBGA is set in accordance with the engine revolution speed, negativepressure in the master vac can be sufficiently ensured.

Furthermore, because the permissible negative pressure for continuationof cylinder deactivation #MPALCS as a threshold for the master vacnegative pressure MPGA is set in accordance with the vehicle speed,negative pressure in the master vac can be sufficiently ensured inaccordance with the vehicle speed.

FIG. 7 shows a flowchart according to another embodiment of the presentinvention. In this embodiment, only the flowchart of the previousembodiment shown in FIG. 5 is substituted by the flowchart shown in FIG.7; therefore, the remaining operations will not be explained again.Because the flowchart of FIG. 7 shows the operation for selecting aircontrol mode along with the flowchart of FIG. 6, reference will be madeto FIG. 6 in the following description. In addition, because most ofFIG. 7 is the same as FIG. 5, the same step numbers are assigned for thesame operations, and only the differences will be explained.

This embodiment significantly differs from the previous one in that anoperation for determining whether the master vac negative pressure MPGAis lower (closer to vacuum) than the permissible negative pressure forcontinuation of cylinder deactivation #MPALCS is included in step S223,as shown in FIG. 7.

In other words, in this embodiment, the secondary air passage 33 isclosed by the control valve 34 only when the master vac negativepressure MPGA is higher (closer to atmospheric pressure) than thepermissible negative pressure for continuation of cylinder deactivation#MPALCS.

Specifically, in step S217, it is determined whether the value of theflag F_DECPBUP is “1”. When the result of the determination in step S217is “YES”, the operation proceeds to step S223, and when the result is“NO”, the operation proceeds to step S218.

In step S222, it is determined whether the engine revolution speed NE isgreater than the threshold #NE which is used for determination ofentering into the deactivation mode. When the result of thedetermination in step S222 is “YES”, which means that engine revolutionspeed is relatively high, the operation proceeds to step S224, and whenthe result is “NO”, which means that the engine revolution speed isrelatively low, the control operation of this flow is terminated. Instep S224, the engine is controlled to enter into the deactivation modein which the control valve 34 is closed; then, the control operation ofthis flow is terminated.

In step S223, it is determined whether the master vac negative PressureMPGA is equal to or lower (closer to vacuum) than the permissiblenegative pressure for continuation of cylinder deactivation #MPALCS.When the master vac negative pressure MPGA is lower than the permissiblenegative pressure for continuation of cylinder deactivation #MPALCS,which means that the master vac negative pressure MPGA is closer tovacuum, the control operation of this flow is terminated. When themaster vac negative pressure MPGA is higher than the permissiblenegative pressure for continuation of cylinder deactivation #MPALCS,which means that the master vac negative pressure MPGA is closer toatmospheric pressure, the operation proceeds to step S224.

Accordingly, in this embodiment, as in the above embodiment, when thevehicle is moderately decelerating, the determination of the cylinderdeactivation, i.e., the operation for determining whether thepre-deactivation conditions permitting the cylinder deactivationoperation are satisfied, as shown in FIG. 2, is performed. In thisprocess, when the intake negative pressure PBGA in the intake passage islower (i.e., closer to vacuum) than the permissible negative pressurefor cylinder deactivation #PBGALCS, the secondary air passage 33 isprepared to be closed (step S143 shown in FIG. 3) in order toefficiently utilize negative pressure in the intake passage for ensuringnegative pressure in the master vac, and the cylinder deactivationoperation is not executed (step S145 shown in FIG. 3 and step S120 shownin FIG. 2).

Upon completion of preparation for closing the secondary air passage 33,it is determined whether the master vac negative pressure MPGA is equalto or lower (closer to vacuum) than the permissible negative pressurefor continuation of cylinder deactivation #MPALCS. When the master vacnegative pressure MPGA is not sufficiently low, i.e., when the result ofthe determination in step S223 shown in FIG. 7 is “NO”, the engine iscontrolled to enter into the deactivation mode (step S224 shown in FIG.6) in which the secondary air passage 33 is closed by the control valve34. Accordingly, negative pressure in the master vac is efficientlyensured by utilizing negative pressure in the intake passage. Whennegative pressure in the master vac is ensured and pressure in theintake passage (intake pressure) is increased, the control operation istriggered by this intake pressure (step S140 shown in FIG. 3), thecontrol valve 34 is closed (step S141 shown in FIG. 3), and the cylinderdeactivation operation is executed (step S142 shown in FIG. 3 and stepS113 shown in FIG. 2). When the cylinder deactivation operation iscancelled through the determination of whether the deactivationcancellation conditions are satisfied (shown in FIG. 4 and step S105shown in FIG. 2), the engine enters into normal operation (step S120shown in FIG. 2). Accordingly, negative pressure in the master vac whichis influenced by the cylinder deactivation operation can be ensured soas to maintain the brake performance while enabling a great improvementin the fuel consumption of the vehicle due to the cylinder deactivationoperation.

As explained above, in this embodiment, because it is directlydetermined whether negative pressure in the master vac is ensured, andthe control valve 34 is closed when negative pressure in the master vacis not ensured (the result of the determination in step S223 shown inFIG. 7 is “NO”), in addition to the advantageous effect in the aboveembodiment, it is possible to operate the control valve 34 in accordancewith the state of negative pressure in the master vac, and to improvereliability.

The present invention is not limited to the above embodiments.Alternatively, for example, the secondary air passage may be closed whenthe intake negative pressure PBGA in the intake passage is lower (i.e.,closer to vacuum) than the permissible negative pressure for cylinderdeactivation #PBGALCS, or when the master vac negative pressure MPGA ishigher (i.e., closer to atmospheric pressure) than the permissiblenegative pressure for continuation of cylinder deactivation #MPALCS.

INDUSTRIAL APPLICABILITY

As explained above, according to the first aspect of the presentinvention, because the control valve operating section operates thesecondary air valve so as to close the secondary air passage when theintake pressure is a negative value lower (closer to vacuum) than thepredetermined first threshold at the instance of starting decelerationtraveling, the intake depression of the engine can be efficientlyutilized to ensure that the negative pressure in the master vac issufficiently low. Accordingly, because pressure in the master vac ismaintained to be sufficiently low, the braking force is sufficientlyassisted even when negative pressure in the master vac is reduced by thebraking operation. Furthermore, fuel consumption is greatly improvedbecause the cylinder deactivation operation is less frequently cancelledand regenerative energy is fully utilized.

According to the second aspect of the present invention, because thecontrol valve operating section operates the secondary air valve so asto close the secondary air passage when the negative pressure in themaster vac is a negative value higher than the predetermined secondthreshold at the instance of starting deceleration traveling, the intakedepression of the engine can be efficiently utilized to decrease thenegative pressure in the master vac to a sufficiently low value.Accordingly, because pressure in the master vac is maintained to besufficiently low, the braking force is sufficiently assisted even whennegative pressure in the master vac is reduced by the braking operation.Furthermore, fuel consumption is greatly improved because the cylinderdeactivation operation is less frequently cancelled and regenerativeenergy is fully utilized.

According to the third aspect of the present invention, because theintake depression of the engine can be efficiently utilized to decreasethe negative pressure in the master vac to a sufficiently low value whenthe negative pressure in the master vac is not sufficiently low prior tothe cylinder deactivation operation, negative pressure in the master vacwhich assists the braking force is ensured prior to the cylinderdeactivation operation so that the braking effort of the operator isreduced.

According to the fourth aspect of the present invention, because thesecondary air valve is closed so that the intake negative pressure canbe ensured to be sufficiently low prior to the cylinder deactivationoperation, it is possible to ensure negative pressure in the master vacprior to the cylinder deactivation operation.

According to the fifth aspect of the present invention, because thepredetermined first threshold is appropriately determined in accordancewith the running speed of the engine, negative pressure in the mastervac can be sufficiently decreased.

According to the sixth aspect of the present invention, because thesecond threshold is appropriately determined in accordance with thetraveling speed of the vehicle, where the second threshold relates tothe negative pressure in the master vac which is utilized to decreasethe traveling speed of the vehicle, negative pressure in the master vaccan be sufficiently decreased in accordance with the traveling speed ofthe vehicle.

According to the seventh aspect of the present invention, becausestopping of the vehicle may be set to have highest priority withoutexecuting the cylinder deactivation operation when the degree ofdeceleration is considered to be great, it is possible to prioritize theoperator's desire.

Explanations of Reference Symbols

11: FIECU (control valve open/close section); 30: intake passage; 33:secondary air passage; 34: control valve (secondary air control valve);E: engine; M: motor; S1: intake negative pressure sensor (intakepressure sensing section) S3: master vac negative pressure sensor(master vac negative pressure sensing section).

1. A control device for a hybrid vehicle having an engine and a motorfor outputting power for driving said vehicle, wherein a regenerativebrake is used during deceleration traveling of said vehicle inaccordance with a deceleration state thereof, and said engine includesat least one deactivatable cylinder which is deactivatable duringdeceleration traveling of said vehicle, said control device comprising:a deactivation determining section for determining whether saiddeactivatable cylinder is allowed to be deactivated in accordance with atraveling state of said vehicle; a deactivation cancellation determiningsection for canceling cylinder deactivation during deactivationoperation; an intake pressure sensing section for measuring air pressurein an intake passage of said engine; and a control valve operatingsection for opening/closing a secondary air passage of said engine forproviding auxiliary air into said intake passage by operating asecondary air valve, wherein said control valve operating sectionoperates said secondary air valve so as to close said secondary airpassage when the intake pressure measured by said intake pressuresensing section is a negative value lower than a predetermined firstthreshold during deceleration traveling of said vehicle.
 2. A controldevice for a hybrid vehicle having an engine and a motor for outputtingpower for driving said vehicle, wherein a regenerative brake is usedduring deceleration traveling of said vehicle in accordance with adeceleration state thereof, and said engine includes at least onedeactivatable cylinder which is deactivatable during decelerationtraveling of said vehicle, said control device comprising: adeactivation determining, section for determining whether saiddeactivatable cylinder is allowed to be deactivated in accordance with atraveling state of said vehicle; a deactivation cancellation determiningsection for canceling cylinder deactivation during deactivationoperation; a master vac negative pressure sensing section for measuringnegative pressure in a master vac which communicates with an intakepassage of said engine and which assists a braking force by means ofintake depression in accordance with a braking operation by an operatorof said vehicle; and a control valve operating section foropening/closing a secondary air passage of said engine for providingauxiliary air into said intake passage by operating a secondary airvalve, wherein said control valve operating section operates saidsecondary air valve so as to close said secondary air passage when thenegative pressure in said master vac measured by said master vacnegative pressure sensing section is a negative value higher than apredetermined second threshold during deceleration traveling of saidvehicle.
 3. A control device for a hybrid vehicle having an engine and amotor for outputting power for driving said vehicle, wherein aregenerative brake is used during deceleration traveling of said vehiclein accordance with a deceleration state thereof, and said engineincludes at least one deactivatable cylinder which is deactivatableduring deceleration traveling of said vehicle, said control devicecomprising: a deactivation determining section for determining whethersaid deactivatable cylinder is allowed to be deactivated in accordancewith a traveling state of said vehicle; a deactivation cancellationdetermining section for canceling cylinder deactivation duringdeactivation operation; an intake pressure sensing section for measuringair pressure in an intake passage of said engine; a master vac negativepressure sensing section for measuring negative pressure in a master vacwhich communicates with an intake passage of said engine and whichassists braking force by means of intake depression in accordance with abraking operation by an operator of said vehicle; and a control valveoperating section for opening/closing a secondary air passage of saidengine for providing auxiliary air into said intake passage by operatinga secondary air valve, wherein said control valve operating sectionoperates said secondary air valve so as to close said secondary airpassage when the intake pressure measured by said intake pressuresensing section is a negative value lower than a predetermined firstthreshold and the negative pressure in said master vac measured by saidmaster vac negative pressure sensing section is a negative value higherthan a predetermined second threshold during deceleration traveling ofsaid vehicle.
 4. A control system as claimed in any one of claims 1 to3, wherein said control valve operating section operates said secondaryair valve so as to close said secondary air passage when cylinderdeactivation is prohibited by said deactivation determining section. 5.A control system as claimed in claim 1 or 3, wherein said firstthreshold is determined in accordance with a running speed of saidengine.
 6. A control system as claimed in claim 2 or 3, wherein saidsecond threshold is determined in accordance with a traveling speed ofsaid vehicle.
 7. A control system as claimed in any one of claims 1 to3, wherein said control system further comprises a deceleration statedetermining section for determining a degree of deceleration of saidvehicle, and wherein said deactivation cancellation determining sectioncancels cylinder deactivation when the degree of deceleration exceeds apredetermined value.